not a gunsmith per say but I was a manual machinist for 5 years and then a millwright for about 30 more. I am using a Manson go gage for setting the barrel, the bolt closes easily now with it in place, take the go gage and put a .002 aluminum shim on the back and bolt will no longer close
when I set that barrel the gage was on back order and I used a piece of Hornady factory ammo to set it. I will not ever make that mistake again. I have a feeling factory ammo is set up a tad on the short side to make sure it chambers in all guns.
BTW your post did give me pause for thought and I just rechecked it for the 4th or 5th time and am satisfied with it